Underwater firing device

ABSTRACT

A MINIATURE UNDERWATER FIRING DEVICE WHICH CAN BE CARRIED BY A SWIMMER AND BE SET OFF BY REMOTE ACOUSTIC CODED SIGNALS. A RECEIVER CIRCUIT COMPRISING A HYDROPHONE, AMPLIFIERS, A BAND PASS FILTER, PARALLEL CONNECTED NARROW BAND CODE FILTERS, LOGIC CIRCUITRY AND AN ACOUSTIC RELAY CONNECTED IN THE SIGNAL PATH.

March 23, 1971 s. o. GARBER 3,572,244

UNDERWATER FIRING DEVICE Filed July 20. 1967 2 Sheets-Sheet 1 In a: o z

O I m w Q i 4?" Q D I C NF i mvsmoa Bruce D. Gerber BY ATTOR Y AGENT United States Patent US. Cl. 102-18 5 Claims ABSTRACT OF THE DISCLOSURE A miniature underwater firing device which can be carried by a swimmer and be set off by remote acoustic coded signals. A receiver circuit comprising a hydrophone, am

plifiers, a band pass filter, parallel connected narrow band code filters, logic circuitry and an acoustic relay c0nnected in the signal path.

BACKGROUND OF THE INVENTION This invention relates to underwater demolition firing devices and more specifically to miniature acoustic demolition firing devices which are remotely actuated.

Acoustic underwater demolition firing devices are known in the art. Previously demolition firing devices have been developed which operate in response to coded acoustic signals to fire an explosive primer. One device in particular comprised a hydrophone, a preamplifier, a band pass filter, driver and logic circuitry, narrow band filters, and an acoustic relay in the signal path. When a predetermined coded acoustic signal was picked up by the hydrophone and passed through the series of amplifiers, filters and logic circuitry, an acoustically actuated relay was activated causing a charged capacitor to discharge an electrical firing pulse into an explosive primer thereby achieving demolition of the device from a remote location. Although satisfactory in many applications, underwater firing devices of the type described were too large and bulky to be carried by an individual swimmer. The hydrophone, filters and battery, for example, were much too large for a small package demolition device of the size which could be readily carried by a swimmer. In addition to the disadvantage of the size of prior art devices for the intended use by individual swimmers, the sensitivity of the receiver circuitry described above was less than desirable. Until the present invention there were no satisfactory underwater acoustic demolition firing devices available which could be easily handled by an individual swimmer.

SUMMARY OF THE INVENTION The general purpose of the present invention is to provide a miniature underwater acoustic demolition firing device having high sensitivity, capable of being easily handled by individual swimmers and of being actuated remotely in response only to a predetermined coded signal.

It is an object of the present invention to provide a novel miniature underwater demolition acoustic firing device.

It is another object of the invention to provide an improved underwater demolation firing device.

The above and other objects are attained by an acoustic firing device having a small hydrophone, band pass filter, and DC. battery with parallel connected split-ring ceramic disc filters connected electrically to the rest of the acoustic signal receiving circuitry and explosive primer actuating means. An improved preamplifier circuit connected to the hydrophone output and the use of parallel connected ceramic filters enable the receiver to have increased sensitivity over larger prior art devices. The present firing device is therefore greatly reduced in size but at ice the same time maintains increased sensitivity over prior art underwater acoustic firing devices.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects, features and attendant advantages will be readily appreciated as the same becomes better understood by the accompanying drawings wherein:

FIG. 1 is schematic circuit diagram of an amplifier used in one embodiment of the invention;

FIG. 2 illustrates a block diagram of the electrical circuit of the invention;

FIG. 3 is a perspective view illustrating the housing of one embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows in detail the preamplifier 13 illustrated in block form in FIG. 2 while FIGS. 2 and 3 are referred to for a general illustration of the invention. In FIG. 2, a hydrophone 11 is shown electrically connected to an acoustic signal receiver which actuates an explosive primer 40 when the appropriate coded signal is received. The entire electrical circuit of FIG. 2 including the hydrophone 11, power source 28 and primer 40 are contained entirely within a small housing such as the one illustrated in FIG. 3.

The incoming acoustic signal is picked up by the hydrophone 11 and amplified by the preamplifier 13. Amplifier 13 is designed to have high sensitivity to the frequency signals in the acoustic range of the band pass filter 15. Filter 15 rejects frequency signals outside the frequencies of interest and passes signals within the band width to driver amplifier 17.

The driver 17 is connected to code filters 19, 21, 23 and 25 which are parallel connected split ring ceramic disc filters and are narrow band filters for resonant frequencies F1, F2, F3 and F4 respectively. The transmitted and code filter frequencies are pre-selected so that code filters 19 and 21 will each pass one of two required frequencies F1 and F2 to actuate the relay in firing network 35. When both frequencies F1 and F2 are passed simultaneously by filters 19 and 21, AND gate 30 in the logic network 26 is biased on thereby passing an activation signal to firing network 35. The unit will not actuate, however, if a signal frequency F3 or F4 is passed by either code filter 23 or 25. OR gate 32 in the logic network is biased on in the presence of signals F3 or F4 if they are of comparable signal strength to signals F1 and F2. A signal passing through OR gate 32 thereby prevents the acoustically activated relay 35 from being activated by unauthorized parties or if safing of the device is desired. When relay 35 is activated, a charged capacitor (not shown) in the acoustically actuated relay network 35 discharges an energy pulse to the primer 40.

Logic network 26 contains transistorized active elements and diode detector circuitry coupled to the ceramic disc filters.

DC. power is supplied to the acoustic signal receiver from the power source 28 which may, for example, contain a grounded center tap 10.8 volt battery made up of 8 Mallory mercury cells. Positive voltage may be supplied over line A through an activation switch 29' to the driver 17 and similarly negative voltage may be provided to amplifier 13 over line B-Bl, to logic network 26 over line B-B2 and firing network 35 over line B-B3.

Activation switch 29 initiates timed elay relay 34. After the predetermined time delay provided by relay 34 has elapsed, the demolition firing device is in condition to receive the acoustic underwater signals.

The device illustrated in block diagram in FIG. 2 is completely housed in the miniature container shown in FIG. 3. An aluminum shell 42 contains all of the demolition receiver circuitry with the exception of the hydrophone which is contained in cylinder 44 and the activation switch (not shown) which may be located on the shell 42 near the hydrophone end. An end coupler 45 is provided for the output of the device. The dimensions of the firing device housing may be approximately 2 inches in diameter for the shell 42 with an overall length including cylinder 44 between 6 inches and 11 inches. Prior art devices used for the same purposes have been larger by a factor of 20, thereby making it very difficult for an individual swimmer to handle.

The amplifier illustrated in FIG. 1 provides improved sensitivity over prior art underwater demolition firing devices. The preamplifier used in connection with the logic circuitry and other receiver elements shown in FIG. 2 has been found to provide up to 12 db greater sensitivity than similar prior art devices.

An input signal received at hydrophone 11 passes through capacitor C1 to the base of input transistor T1 for first stage amplification. Diodes D1 and D2 are oppositely poled voltage limiting diodes connected in parallel with the input hydrophone 11. Transistor T1 has its base connected to voltage divider resistor R1 and R2 and its emitter connected to resistor R3. The output signal from transistor T1 is passed to transistor T2 from the emitter of transistor T1 and the base of transistor T2 for the first stage amplified output.

Transistor T2 is connected to second stage amplifiers T3 and T4 from the collector of transistor T2 to the base of transistor T3. The emitter of transistor T2 is connected to an RC network comprising resistor R4 in series with parallel connected resistor R5 and capacitor C2.

The emitter of transistor T3 and base of transistor T4 are connected to resistor R7 in the second stage and the emitter of transistor T4 is coupled to parallel connected resistor R9 and capacitor C3.

The amplified output signal is derived from transistor T5 at the emitter connected capacitor C5. The emitter is also connected to resistor R10. A filter capacitor C4 is connected between the common wire and resistor R11.

DC. current is supplied through resistors R11 and R1 to the base of transistor T1, through resistors R11 and R6 to the collector of transistor T2 and base of transistor T3, through resistors R11 and R8 to the collector of transistor T4, and through resistor R11 to the collectors of transistors T1, T3 and T5.

From the foregoing description of a preferred embodiment of the invention, it is apparent that a new and improved miniature underwater demolition acoustic signal firing device has been developed which can be easily carried by a single swimmer, activated remotely by coded acoustic signals, and which is improved in sensitivity and size limitations from similar pror art devices. It should be understood, of course, that the embodiment disclosed is merely illustrative and not intended to limit the scope of the invention. Reference should be made to the appended claims, therefore, rather than the specification as indicating the scope of the invention.

What is new and desired to be secured by Letters Patent of the United States is:

1. A miniature underwater demolition firing device comprising in combination, housing means containing therein:

means for receiving acoustic signals and for generating electrical representative signals thereof;

amplifier means electrically coupled to said acoustic signal receiving means for amplifying said electrical representative signals in a predetermined frequency range;

a plurality of split ring ceramic disc narrow band filters coupled to said amplifier means, each of said ceramic filters resonant to a different predetermined frequency;

an acoustically actuated relay network;

a source of electrical energy for providing a firing pulse upon said relay network being actuated; and

multiple input logical gating means connected between said ceramic disc filters and said relay network for passing an actuation signal to said relay network in response to the reception of predetermined coded frequency signals by said acoustic receiving means.

2. The apparatus of claim 1 further comprising in said housing means,

an activating switch electrically connected to said source of electrical energy, and

time delay means coupled between said activating switch and said relay network for delaying said firing pulse a given amount of time after the reception of said predetermined coded signals.

3. The apparatus of claim 1 further comprising an explosive primer connected electrically to said relay network.

4. The apparatus of claim 1 wherein said ceramic disc filters are connected in parallel; and said amplifier means includes a transistorized preamplifier connected to said acoustic receiving means, said acoustic receiving means being a hydrophone, a band pass filter connected to the preamplifier, and a driver amplifier connected between said band pass filter and each of said ceramic disc filters.

5. The apparatus of claim 2 wherein said housing means is a cylindrical-like shaped container which is approximately 2 inches in diameter and between the range of 6 inches to 11 inches in length.

References Cited UNITED STATES PATENTS 2,489,255 11/1949 Barker 102-70.2 2,987,700 6/1961 Hawkins 10218X 3,012,503 12/1961 Brown et al. 102-18 3,100,444 8/1963 Ball et al. 10221.6 3,110,877 11/1963 Fisher et al. 102l 8X 3,125,953 3/1964 Foerster 102-48 3,293,676 12/1966 Link 102-18X VERLIN R. PENDEGRASS, Primary Examiner 

